In recent years, a system or apparatus in which a plurality of display devices and display terminals perform video display in cooperation with one another has been widespread in the fields of video education and presentation. Patent Document 1 is one of techniques for such a video system. Patent Document 1 discloses that a movable pointer graphic is displayed on a lecture material on a terminal of a lecturer, and the same action as that made by the pointer graphic on the lecture material on the terminal of the lecturer is reproduced in real time on a lecture material displayed on a terminal of a participant.